1. Field of the Invention
The present invention generally relates to a battery powered motor assembly, and more specifically to a battery powered motor assembly comprising a motor casing to fixedly retain a motor therein and a battery casing to fixedly retain a battery therein, the motor and battery casings being rotatably connected together, the battery casing being covered airtightly with a partition wall so as to be explosion-proof to enable the motor assembly to house a battery, such as a nickel-cadmium battery, which may discharge hydrogen gas.
2. Description of the Prior Art
Most conventional battery-powered motor assemblies have such a construction that a motor casing to fixedly retain a motor and a battery casing to fixedly retain a battery are rotatably connected together at their ends and a motor switch is turned on and off by the relative rotation of the motor and battery casings. This type of motor assembly has many advantages including that the motor and battery are axially aligned and that the switchings portion of the motor assembly is not externally exposed.
However, the positive terminal of the battery ohmically contacts one terminal of the motor, and a contact strip extending from the negative terminal of the battery ohmically contacts the other terminal of the motor. To attain this, an end face of the motor casing abuts with one end face of the battery casing without any partition wall between them.
Nickel-cadmium batteries have been widely used in recent years. Batteries of this type have an extremely low internal resistance and can easily discharge several amperes of current. In addition, even after they have been discharged to zero terminal voltage, batteries of this type can be quickly recharged in several minutes.
However, if batteries of this type, which usually have escape valves for releasing gas generated during overcharging, are housed in an electric appliance before gas release is completed, the battery compartment becomes filled with gas, mainly hydrogen gas, threatening an unwanted explosion. Therefore, it is desired to make the battery casing explosion-proof.
Particularly, when such a battery is used to power a submersible type motor, a explosion-proof measures are required for the battery casing which is of a watertight construction.